INFLUENCE ON ANTIBODY RECOGNITION OF AMINO-ACID SUBSTITUTIONS IN THE CLEFT OF HLA-DQ2 MOLECULES - SUGGESTIVE EVIDENCE OF PEPTIDE-DEPENDENT EPITOPES

The purpose of this study was to identify polymorphic residues of DQ2 beta chains which are involved in the epitopes recognized by DQ2-react ive mAbs. Binding studies were performed on a panel of DQ2 mutant cell s made by transfection of a DQ (alpha 10501,beta 1*0301)-positive B-L CL with DQB1 genes encoding either wiId-type or mutated DQ beta 10202 . Several aa substitutions were found to influence the binding of DQ2 mAbs. All but one of the mAbs were clearly sensitive to the introduced aa substitutions, but individual mAbs were differentially influenced, suggesting that they recognized different epitopes on the DQ2 molecul e. Substitutions in positions 30 and 37 of the peptide-binding cleft w ere also found to influence the binding of some mAbs. Second, two mAbs , NFLD.M71 and NFLD.M102, which bound to DQ(alpha 10501,beta 1*0202) expressed in human cells and were sensitive to the introduction of aa substitutions in che cleft, bound weakly to the DQ(alpha 10501,beta 1 0202) heterodimer when expressed in a transfected murine NIH 3T3 cell line. Together this indicates that some DQ2-reactive mAbs may recogni ze peptide-dependent epitopes.